Abstract: In order to investigate the mechanical properties, damage mode and energy evolution of loess-slag-based cementitious filling materials under different water-cement ratios and curing ages, slump tests and uniaxial compression tests were conducted on loess-slag-based cementitious filling materials under four sets of water-cement ratios and five ages, respectively. It was found that the slump and expansion of the filling material increased with the increase of water-cement ratio. The peak strength of the material was negatively linearly correlated with the water-cement ratio and exponentially nonlinearly correlated with the age of curing. The damage mode of the filling material was generally shear damage, and the smaller the water-cement ratio and the longer the age of curing, the greater the damage of the filling material. The damage process of cemented material can be divided into five stages: compression density, elasticity, stable crack expansion, continuous crack expansion and post-peak damage.